The present invention relates to a rubber composition for an inner liner and a tire comprising thereof.
Butyl rubbers such as a butyl rubber and a chlorinated butyl rubber, carbon black and the like have been conventionally used as the compounding agent of a rubber composition (a rubber composition for an inner liner) used for production of the inner liner of a tire, but recently environmental problems have been taken very seriously, the regulation of suppressing the emission of CO2 is strengthened, and petroleum raw materials are limited and the supply amount is decreased year by year; therefore there is a limitation to use the compounding agent consisting of petroleum resources such as the butyl rubbers and carbon black.
Accordingly, suppose that petroleum are exhausted in the future, it will be necessary to use resources other than petroleum such as a natural rubber and white fillers such as silica and calcium carbonate as the compounding agent of a rubber composition for an inner liner.
However, when a compounding agent obtained from resources other than petroleum is compounded with a rubber composition for an inner liner, viscosity of kneaded products is increased in a kneading step of the rubber composition because silica having higher viscosity than carbon black is compounded and sufficient kneading cannot be carried out; therefore there has been a problem that processability of rubber compositions is lowered. Further, there has been a problem that rolling resistance of a tire having an inner liner comprising the rubber composition is also increased (rolling resistance property is lowered).
It is carried out that a processing aid for silica of surfactants such as a metal salt of fatty acid is compounded together with silica in order to reduce viscosity of kneaded products to improve processability in a kneading step, but since the processing aid is obtained from petroleum resources, there is a fear of being unable to be used in the exhaustion of petroleum.
A rubber composition for an inner liner is disclosed in the Japanese Unexamined Patent Publication No. 2004-339288, but the composition is not a composition wherein compounding silica and a large amount of carbon black is further used; therefore there has been a problem that it cannot be adapted to the exhaustion of petroleum.